One such vane pump is known from U.S. Pat. No. 2,318,292.
German Offenlegungsschrift No. 40 11 671 also describes a vane pump which has substantially the above mentioned features, but the arrangement and position of possible adjustment members is not described. Apart from the special arrangement of adjustment members and corresponding design of the controlling collar, the vane pump described in DE 40 11 671 Al is identical with the vane pump described in the present application so that that application, which originates from the same inventor, may be referred to as regards further design features and properties associated therewith.
The adjustment members require a large space as is shown by the nearest prior art represented by the above mentioned U.S. Pat. No. 2,318,292. Because such vane pumps are regularly used as auxiliary units for other machines, particularly as lubricating pumps in engines and other machines, the utilization of additional space is undesired and often associated with considerable drawbacks. In addition, also the weight of the pump is thereby increased which is also undesirable. Finally, the control ducts for the adjustment member or members require additional holes or passages in the casing to enable the mentioned pumping parameters to act on the adjustment members which, in turn, change the position of the controlling collar and thereby the parameter of the pump to a desired value.